In-cell solvent fire has been treated globally as a typical accident of a reprocessing plant. In order for the fire to break out, leakage of a significant amount of solvent, a temperature rise above its flash point, and the presence of ignition source have to occur simultaneously. In this paper, such an accident was analyzed from a probabilistic viewpoint. The occurrence frequency was shown to be 10−7/y because a frequency or probability of each event is so small. Nevertheless, we assumed the fire occurring for 1 h. One hour should be enough for the assessment of the consequence because an operator can implement measures to extinguish the fire by inducing oxygen deficiency in the cell, such as closing a fire damper or stopping the exhausting fan. Since a certain amount of soot produced by fire does not deteriorate the function of a HEPA filter, the effective dose for the general public is less than 0.1 mSv. The results will be useful for judging the safety importance level of the safety measures against fire.
